Scientific Method —

Imaging the brain of a shopper

Researchers track the brain activity of people doing some simulated shopping, …

What goes into buying something? At the border between economics and neuroscience, researchers have started to use functional MRI to determine the areas of the brain that become active when financial decisions are made, such as how to invest money. Now, a study has turned those methods to a simplified shopping process, and found a pattern of brain activity that can accurately predict purchase decisions.

The work relied on a three-stage shopping test. Test subjects were first shown an image of a product for four seconds. The product and its price were then shown together for four seconds, after which the subject had four seconds to register a purchase decision. Meanwhile, brain activity was being tracked using the fMRI. Three areas of the brain drew the researchers' attention: the nucleus accumbens (NAcc), which is associated with reward anticipation, the mesial prefrontal cortex (MPFC), which registers perceived gains, and the insula, which anticipates pain and other negatives.

Each of these areas displayed a distinct activity pattern during the shopping process. In purchasers, the NAcc anticipated a gain, and got active when the product was revealed, staying high until decision time. It stayed mostly flat in non-buyers. The MPFC of purchasers started rising when the price was revealed and peaked in decision time (consistent with sensing a gain), whereas it actually dropped when the price was revealed to those who weren't buying. The activity in the insula, which anticipates pain, actually dropped during the reveal phase in all cases, but in non-buyers, it rapidly came back up and was activated during the purchase phase.

The researchers then repeated the tests with new subjects, and then checked whether they could use these activity patterns to predict whether they had bought. Their model was better at predicting a purchase than the self-reported evaluations of the test subjects. This is clearly a simplified situation—probably most similar to an impulse buy—but it suggests that even rapid purchase decisions are driven both by the general appeal of a product and by whether you perceive its price as appropriate. And that pain you feel in your wallet? It might not be as metaphorical as we think.